Part of #9744

Removes all redundant `# -*- coding: utf-8 -*-` lines from files, as python 3 automatically reads source code as utf-8 now.

`Signed-off-by: Jonathan de Jong <jonathan@automatia.nl&gt;`>

This is done by creating a custom `RedisFactory` subclass that
periodically pings all connections in its pool.

We also ensure that the `replyTimeout` param is non-null, so that we
timeout waiting for the reply to those pings (and thus triggering a
reconnect).

This expands the current shadow-banning feature to be usable via
the admin API and adds documentation for it.

A shadow-banned users receives successful responses to their
client-server API requests, but the events are not propagated into rooms.

Shadow-banning a user should be used as a tool of last resort and may lead
to confusing or broken behaviour for the client.

We were running some linters on some files and some on others. Extract a common
setting and use it everywhere.

I'm going to be doing more stuff synchronously, and I don't want to lose the
CPU metrics down the sofa.

We forgot to set the password on the subscriber connection, as well as
not calling super methods for overridden connectionMade/connectionLost
functions.

This is configured via the `redis` config options.